Build 9: QR scan, camera fixes, first-run onboarding, sweep fixes

Camera/QR (validated live with a v4l2loopback virtual camera):
- decode non-MJPEG frames on Linux (raw YUYV was undecodable: eternal
  spinner), enumerate devices off the UI thread without unwrap, open
  cameras by their real device index (list position broke whenever
  /dev/video0 was absent), show "No camera found" after 5s
- scan-to-pay: QR button in the send recipient search row and the
  mobile home header; in-surface camera panel feeding recipient
  resolution; only text payloads accepted (seeds/slatepacks refused)
- receive QR was unscannable: full cells (0.5px gaps fragmented finder
  patterns at 4.5px cells), always ink-on-white plate (inverted codes
  fail many scanners), center mark 26% -> 19% (zbar chokes above);
  rqrr+zbar both decode the live card now; unit tests cover the exact
  widget geometry

First-run onboarding (replaces the stock empty state only; the wallet
list, add-wallet modal and GRIM creation flow stay for later wallets):
- intro -> node choice (Private integrated / Instant external with
  URL) -> create or restore (wraps MnemonicSetup; word grid, paste,
  SeedQR scan) -> optional @username claim with prominent skip
- fonts bind at creation context so frame one can use Geist families

Sweep fixes (22 confirmed findings, the simple ones):
- yellow theme: active sidebar nav was dark-on-dark (P1)
- window frame ring painted with theme bg: transparent clear color
  rendered as a black band without a compositor (P2)
- import/rotate identity inputs get visible field wells (P2)
- receive buttons: verb labels + transient "Copied" feedback
- review hero card fills the column; fee row copy; pay-tab stale and
  duplicated hints; unlock modal copy; node card subtitle truncation
- build number stays current (.git/logs/HEAD rerun trigger)

Backup restore: import accepts the export-time password and re-encrypts
under the current wallet password; cross-device restores work.

31 lib tests green. Mainnet-validated: both flows restored real
wallets; 0.1 grin sent B->A through NIP-17 over Tor with async
open/close ping-pong; tx 71fbfce4f591 posted on-chain.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/gui/platform/desktop/mod.rs

@@ -62,17 +62,22 @@ impl Desktop {
 		use nokhwa::Camera;
 		use nokhwa::pixel_format::RgbFormat;
 		use nokhwa::utils::ApiBackend;
-		use nokhwa::utils::{CameraIndex, RequestedFormat, RequestedFormatType};
-
-		let devices = nokhwa::query(ApiBackend::Auto).unwrap();
-		cameras_amount.store(devices.len(), Ordering::Relaxed);
-		let index = camera_index.load(Ordering::Relaxed);
-		if devices.is_empty() || index >= devices.len() {
-			return;
-		}
+		use nokhwa::utils::{FrameFormat, RequestedFormat, RequestedFormatType};
 
 		thread::spawn(move || {
-			let index = CameraIndex::Index(camera_index.load(Ordering::Relaxed) as u32);
+			// Device enumeration does IO — keep it off the UI thread, and
+			// treat a backend error the same as "no cameras".
+			let devices = nokhwa::query(ApiBackend::Auto).unwrap_or_default();
+			cameras_amount.store(devices.len(), Ordering::Relaxed);
+			let index = camera_index.load(Ordering::Relaxed);
+			if devices.is_empty() || index >= devices.len() {
+				return;
+			}
+
+			// Open by the enumerated device's own index, not the list
+			// position: on v4l they differ whenever /dev/video0 is absent
+			// (first camera at video1, loopback-only setups, …).
+			let index = devices[index].index().clone();
 			let requested =
 				RequestedFormat::new::<RgbFormat>(RequestedFormatType::AbsoluteHighestFrameRate);
 			// Create and open camera.
@@ -89,9 +94,29 @@ impl Desktop {
 						}
 						// Get a frame.
 						if let Ok(frame) = camera.frame() {
-							// Save image.
-							let mut w_image = LAST_CAMERA_IMAGE.write();
-							*w_image = Some((frame.buffer().to_vec(), 0));
+							// Consumers expect an encoded image. MJPEG frames
+							// already are; anything else (YUYV, NV12, …) must
+							// be decoded to RGB and re-encoded, or the readers
+							// fail on the raw buffer and show a spinner forever.
+							let bytes = if frame.source_frame_format() == FrameFormat::MJPEG {
+								Some(frame.buffer().to_vec())
+							} else if let Ok(image) = frame.decode_image::<RgbFormat>() {
+								let mut bytes: Vec<u8> = Vec::new();
+								image
+									.write_to(
+										&mut std::io::Cursor::new(&mut bytes),
+										image::ImageFormat::Jpeg,
+									)
+									.ok()
+									.map(|_| bytes)
+							} else {
+								None
+							};
+							if let Some(bytes) = bytes {
+								// Save image.
+								let mut w_image = LAST_CAMERA_IMAGE.write();
+								*w_image = Some((bytes, 0));
+							}
 						} else {
 							// Clear image.
 							let mut w_image = LAST_CAMERA_IMAGE.write();
@@ -99,7 +124,7 @@ impl Desktop {
 							break;
 						}
 					}
-					camera.stop_stream().unwrap();
+					let _ = camera.stop_stream();
 				};
 			}
 		});